Hydraulic control system for a metal forming press

ABSTRACT

There is disclosed a hydraulic control system for use in combination with a metal forming press. The hydraulic control system is adapted to exert a pressure on the frame, the bed and the crankshaft of the metal forming press which is sufficient to carry the tonnage of the press during normal operation and which is sufficient to secure the bed and the crankshaft to the frame.

United States Patent Grankowski et al.

[ June 13, 1972 [54] HYDRAULIC CONTROL SYSTEM FOR A METAL FORMING PRESS [72] Inventors: Eugene E. Grankowski; Lambros A. Pappas, both of Chicago, Ill.

[73] Assignee: Wyman-Gordon Company, Worchester,

Mass.

[22] Filed: July 16,1970

[21] Appl.No.: 55,467

52 u.s.c|....; .72/455 511 Int.Cl. ..1121 9/02 [58] Field of Search ..72/432, 453, 455, 456; 100/52, 100/214; 308/9 [56] References Cited UNITED STATES PATENTS 2,225,761 12/1940 Asbridge ..308/9 2,584,770 2/1952 Wilcock ..308/9 2,770,342 1 H1956 .lohansen 192/150 2,936,055 5/1960 Kassnel 192/129 2,937,606 5/1960 Paulton ..72/432 3,041,899 7/1962 Benninghoff .....72/432 3,130,628 4/1964 Blinn ..100/214 3,160,089 12/1964 Platou..... ...100/2l4 3,426,873 2/ 1969 Tezuka ..100/53 Primary Examiner-Charles W. Lanham Assistant ExaminerGene P. Crosby Attorney-Hume, Clement, Hume & Lee

, [57] ABSTRACT There is disclosed a hydraulic control system for use in combination with a metal forming press. The hydraulic control system is adapted to exert a pressure on the frame, the bed and the crankshaft of the metal forming press which is sufficient to carry the tonnage of the press during normal operation and which is sufficient to secure the bed and the crankshaft to the frame.

16 Claims, 5 Drawing Figures 1590M I/E 0/6 PVMP HYDRAULIC CONTROL SYSTEM FOR A METAL FORMING PRESS BACKGROUND OF THE INVENTION forging operation, there is a stress built up in the frame as the dies mate and the workpieces forge, and a corresponding stress release as the dies part. The frame is thus cyclically stressed and unstressed. As such, the frame is stressed in tension in reaction to the forging loads. The stress variation is commonly referred to as stress excursion.

The end result of excessive cyclical stress excursion is rapid metal fatigue in the critical side housing area of the frame and thus, the possibility of becomes a real problem.

A second problem that exists in large forging presses is that the machine .may be subjected to eccentric loads and the forces developed on one side of the press would differ greatly from vthe forces. developed on the other side of the press closest to the load.

l-leretofore, it has not been possible to develop a press capable of forging large parts such as crankshafts or the like, with pressures up to and in excess of 16,000 tons. This was due in most part to the inability of providing an economical-frame which would be able to withstand such loads and which would not fatigue. Furthermore, it has not been possible heretofore to develop such a press due to the lack of a suitable overload control system. The present invention fulfills this need and enables the manufacture of a large forging press capable of developingpressures in excess of 16,000 tons. For example, utilizing the instant invention, a press may be built having an overall height of less than 50 feet and have a rating in excess of 16,000 tons.

SUMMARY OF THE INVENTION vention contemplates a unique. arrangement whereby the press bed is movably engaged withthe frame through the use of an upper and lower bearing assembly wherein one of the assemblies is hydraulically controlled and where the crankshaft is movably connected to the frame through the use of a similar set of bearing assemblies, again having one of these assemblies being hydraulically controlled.

By utilizing these bearing assemblies and their associated hydraulic control, the present invention enables the preloading of the critical side housing area of the frame thereby increasing fatigue strength due to the drastic reduction of stress excursion. Moreover, the instant invention assures the uniform load distribution in the side housing place by incorporating a hydraulic system to serve the two-fold purpose of preloading and providing overload protection between the press bed and the frame. Lastly, overload protection is achieved as an integral part of the jointbetween the press bed and the side frame housing. This overload protection adds to the overall rigidity of the press frame.

It is, therefore, an object of the present invention to provide a hydraulic means for prestressing certain critical areas of the frame of a metal forming press.

Anotherobject is to provide a means for prestressing the critical areas of the frame of a metal forming press without utilizing tie rods.

A further object is the provision of a hydraulic control system for movably connecting the press bed with the frame of the press. 7 g 7 Still another object is the provision of a hydraulic control for prestressingthe frame wherein the crankshaft of the press may be supported by utilizing a one-piece bearing.

frame failure due to fatigue factors therein creating excessive stresses in one side of the frame H Yet another object is the provision of an assembly which can be slipped on the ends of a crankshaft when assembling the crankshaft and which may be easily engaged with the frame of the press.

Yet another object is to provide a hydraulic system for prestressing the frame of a metal forming press and reducing stress excursion at the frame critical area which wouldotherwise cause fatigue failure of the frame.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE'DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGS. land 2, which illustrate a preferred embodiment, a metal forming press 10. The press 10 comprises a crankshaft 12, a slide or ram 14, a frame 16, and a press bed 20. Frame 16, in the preferred embodiment, comprises several laminated side frame members 18. However, it will be recognized by one skilled in the art that the instant invention need not be utilized with laminated side frame members and may instead utilize side frame members of unitary construction. A space 24 is provided to place the die and die shoe assembly. The space 24 is located between the side frame 16, the slide 14, and a bolster 15. A pair of apertures 25 are provided in the side frame 16 to support the press bed 20 and likewise, a pair of apertures 72 are also provided in the frame 16 to support the crankshaft 12.

Press bed 20, in the preferred embodiment, comprises two ends 21, each having an upper side 22 and a lower side 23. The two ends 21 of press bed 20 are necked down sufficiently to be freely received by apertures 25. The ends of press bed 20 are supported in frame 16 by a press bed bearing support assembly 11 comprising a pair of upper and lower bearing assemblies 26 and 36, respectively. Similarly, crankshaft 12 is supported in frame 16 by a crankshaft bearing support assembly 7l.

Referring now to FIG. 3, upper bearing assembly 26 and lower bearing assembly 36 of the press bed bearing support assembly 11 will be described in more detail. It will be recognized by one skilled in the art that an' upper and lower bearing assembly is utilized on each side of press bed 20. The upper bearing assembly 26 comprises a segmentally spherical upper bearing member 28 having an upper surface 29 and a lower surface 30. The lower surface 30 of the upper bearing member 28 is generally planar and rests on the top surface 22 of the press bed 20. The upper surface 29 of the bearing member 28 is spherical and placed in engagement with a corresponding spherical lower surface 33 of a bearing holder member 31. The bearing holder member 31 abuts the side frame 16 of the press in the top side of aperture 34 (shown in FIG. 1) which is provided in the frame 16. The upper bearing assembly 26 therefore provides the upper part of the movable connection between the press bed 20 and the frame 16.

The lower bearing assembly 36 comprises a bearing member 38 having an upper surface 39 upon which the bottom surface 23 of the press bed 20 rests. In the preferred empreferred embodiment of the bodiment, the spherical bearing member 38 is segmentally spherical at the bottom side and rests upon a piston 44 which has an upwardly facing corresponding segmentally spherical cavity in its upper surface 45. It will be noted that lower surface 40 of the bearing member 38 has been cut away in order to minimize friction drag during movement of the press bed and therefore the bearing member 38 rests directly on the piston 44 only over limited area 41, thereby providing very little friction. The piston 44, in turn, is carried in a lower bearing support member 48 having an upper surface 49 in which a cavity is present and a lower surface 50 which rests against the lower portion of an aperture 42 (shown in FIG. 1) which is provided in the frame 16. It will be noted that the general shape of bearing member 38, lower bearing support member 48, and piston 44 provides two chambers 54 and 56 which may be adapted to convey a fluid under pressure.

The hydraulic chamber 54 is formed between the piston 44 and the bearing member 38. The hydraulic chamber 56 is formed between lower bearing support member 48 and the lower surface 46 of the piston 44. A bleed passage or third hydraulic chamber 58 is provided in the piston 44 to connect the two hydraulic chambers 54 and 56 so that the pressures in the two chambers are essentially the same. As will be explained below, the hydraulic chambers 54 and 56 are adapted to contain a hydraulic fluid pressure sufiiciently high to carry the rated tonnage of the press when the ram 14 is actuated without the upper bearing assembly 26 getting loose.

The areas of the hydraulic chambers 54 and 56 are designed such that the area subjected to hydraulic pressure in the chamber 56 is slightly larger than the effective piston area within the chamber 54. This is necessary when pressurizing the chambers for otherwise the pressure would lift the bearing member 38 off the piston 54 on which it is resting. The slight pressure area differential between the chambers 54 and 56 greatly minimize the contact force which will cause drag or friction during movement of the press bed ends 21. In essence, the hydraulically induced force on the bottom side of piston 44 is slightly greater than the top side, thus allowing the bearing member 38 to be held in place and be almost entirely hydraulically supported. Although a very small spherical surface 41 of the bearing member 38 actually engages the spherical surface 45 of the piston 44, even this small surface would be very difficult to lubricate under the extremely high forces developed in a press of this size, if it were not for the hydraulic support of the bearing member 38.

The hydraulic chamber 56 is connected by means of a fourth hydraulic chamber or passage 60 to an overload valve 62 and to an accumulator 64. It will be recognized that the specific construction of overload valve 62 and accumulator 64 is not critical insofar as the invention is concerned. However, in the preferred embodiment, the overload valve 62 is a nitrogen actuated overload valve and the accumulator 64 is an air-to-oil booster. The primary purpose of these two members is to provide a hydraulic accumulator system which subjects the chamber 56 to a relatively high hydraulic pressure sufficient to carry the tonnage of the press under normal operation. The accumulator 64 provides the function of preventing small press overloads and frame damage. When substantial overload is encountered, the overload valve 62 opens to discharge the pressurized oil and rapidly reduce the pressure so that the press bed bottoms when the bottom of the piston 44 strikes the bottom of the chamber 56. The chambers 54 and 56 are pressurized at all times except when the oil is dumped as a result of a substantial overload. Immediately after the cause of the overload is eliminated the hydraulic system is again brought up to pressure before the press 10 cycles again.

Again referring to FIGS. 2 and 3, the hydraulic control system will be explained in more detail. As mentioned above, the hydraulic control system is designed to protect the press from overload and to provide a movable connection between the press bed 20 and the frame 16. The system will sense the tonnage applied to the press and will actuate the overload valve when the tonnage exceeds the rated press tonnage at either the block or finish die stations. Due to the nature of forging operations and unbalanced loading, it is necessary that the system be actuable by either of the two overload pistons 44. Therefore, an uneven pressure will actuate either or both of the pistons 44, thereby providing a signal which will then disengage the press drive.

As explained above, in an exemplary embodiment the hydraulic system comprises a pair of pistons 44 mounted in the frame 16 of the press. The pistons may be designed such that their normal working stroke is approximately one-quarter of an inch and that the total stroke is 1 inch. This additional stroke is provided in order to unstick the press should the press be stuck near the bottom. During normal operation, the pistons 44 are maintained under rated pressure which will lock the press bed 20 between the pistons 44 and the frame 16. The chambers 54 and 56 are precharged to a hydraulic pressure in excess of the rated pressure corresponding to press rated load. The additional pressure will minimize bed movement as press is loaded to its rated capacity. The chambers 54 and 56 are directly connected to an air-to-oil booster or accumulator 64 and an overload control valve 62. The accumulator 64 will maintain constant pressure on the pistons 44 and will react first to an overload condition before the overload control valve 62. During press overload, the fluid in the chambers 54 and 56 will be decompressed through the overload control valve 64 and the piston 44 will be forced to collapse downwardly towards surface 49. The accumulator will accept the discharged fluid from chambers 54 and 56 only after the press has been subjected to 5 percent in excess of the press rated tonnage. The accumulator or air-to-oil booster 64 will continue to accept the fluid until the pressure equals a capacity approximately 16 percent over the rated tonnage of the press. The overload control valve 62 will then sense this pressure and cause a decompression of fluid from the chambers 54 and 56 on both sides of the press 10.

Referring to FIG. 2, it can be seen that the hydraulic control system receives its fluid from any conventional air-oil pump. Pressure and distance switches may be provided which would serve as an electrical signal to the press control to disengage the clutch when the overload control valve 62 is actuated. This switch is schematically shown as switch in FIG. 2. The accumulator 64 in the preferred embodiment may comprise a pneumatic chamber 66 and a hydraulic chamber 68 and as explained above, is used to absorb the changes in fluid due to the increased pressure.

It will be recognized by one skilled in the art that the utilization of this hydraulic control system enables the press bed 20, supported by upper bearing assembly 26 and the lower bearing assembly 36 to accommodate slight movement of press bed 20 with respect to the frame 16. It will be recognized that such a movable connection is a great improvement over the rigid connection heretofore utilized. Moreover, when the system is pressurized, the various bearing members exert a static load slightly greater than the total press tonnage against the apertures 34 and 42 in the frame, thereby insuring that the laminated side frame members 18 are held, with respect to one another and with respect to the press bed 20, more positively and securely than they could be so held by any mechanical fastening means such as a tie rod.

Furthermore, since the frame members 18 are subjected to an almost steady load at the critical areas, i.e., where the press bed 20 and the crankshaft 12 are each connected to the frames, at all times during the press operation, the critical stress excursion in the frame 16 is drastically reduced. If it were not for the preload provided by the hydraulic control system, the stress in each frame member at the critical areas would change from zero to a maximum value corresponding to one-half the total press tonnage during each full load cycle of the press. This uncontrolled change in stress, or stress excursion, with each stroke of the press would demand a larger press frame of higher strength material to prevent fatigue failure in the frame 16. The utilization of the hydraulic system results in savings in the size of the press and improves the frame strength reliability.

Referring again to FIGS. 1 and 2, a similar hydraulic bearing system will be described in relationship to a crankshaft bearing support assembly 71 for securing the crankshaft 12 to the frame 16. Itwill be readily seen, that this construction is very similar to the construction described above with regard to the press bed bearing support assembly 11 and differs mostly in that no overload control is present. The crankshaft hydraulic bearing support assembly 71 comprises a pair of lower bearing assemblies 80 and a pair of upper bearing assemblies 90. Upper bearing assembly 90 and lower bearing assembly 80 enclose a one-piece bearing 78 which in turn supports the crankshaft. The use of a one-piece bearing to support the crankshaft is a vital factor when utilizing a large capacity press. The crankshaft bearing support assembly 71 is positioned in a pair of apertures 72 provided in the frame 16.

Referring now to FIGS. 4 and 5 as well as l and 2, it will be seen that crankshaft bearing 78 comprises an outer spherical surface which engages corresponding spherical cavities in the lower and upper bearing assemblies 80 and 90. The inner surface of the crankshaft bearing 78 is circular and conforms to the shape of the crankshaft 12. In a preferred embodiment, the crankshaft bearing 78 is bronze but it will be recognized by one skilled in the art that any suitable material may be utilized.

Each lower bearing support assembly 80 comprises a bearing support member 82. The upper surface 81 of the bearing support member 82 comprises a cavity 84 which is shaped to conform to the spherical shape of the outer surface of the crankshaft bearing. 78. The outer surface 83 of crankshaft bearing 78 is spherically shaped and engages upper surface 85 of the bearing support member 82. The upper surface 85 of the bearing support 82 comprises a cavity shaped to accept the spherical surface 83 of the crankshaft bearing 78. The lower surface 86 of the bearing support member 82 is adapted to engage an aperture 88 which is provided in the frame 16 (FIG. 1).

The upper bearing assembly 90 is comprised of a bearing support member 92 and a bearing frame engagement member 94. The bearing support member 92 comprises a lower surface 91 having a cavity therein which is shaped to conform to the outer surface of the crankshaft bearing 78. The bearing frame engagement member 94 comprises an upper surface 96 which is adapted to engage an aperture 98 which is provided in the frame 16. The lower surface 95 of the bearing frame engagement member 94 comprises a cavity therein. A hydraulic pressure chamber 100 is formed between this cavity and the slight space left when bearing frame engagement member 94 and the bearing support members 92 are brought in close relationship to each other as shown in FIG. 4. A hydraulic pressure preload is maintained at all times within chamber 100 of sufficient magnitude to impose a load greater than the total tonnage of the press. To insure that the crankshaft bearing 78 is held between the bearing support member 82 and the bearing support member 92 without gapping or opening under a load, the parts are constructed so that an initial slight clearance of a few thousandths of an inch separates the opposed surfaces of the bearing support members 82 and 92. This slight gap is indicated by numeral 93. Gap 93, however, closes when the members engage and when the hydraulic preload pressure is imposed into the cavity 100. Thus, the bearing 78 is completely confined between the two support bearings 82 and 92 which are held together with a force greater than the maximum force to be exerted through the crankshaft 12, and, therefore, the two bearing support members 82 and 92 will not separate even under slight press overload. This is important because otherwise bearing support members 82 and 92 would separate under a load thereby resulting in unpredictable surface contact between the crankshaft bearing 78 and the upper bearing assembly 90.

The crankshaft bearing support system 71 allows the use of a one-piece crankshaft bearing 78, a vital factor under the loads contemplated. It will be seen that the bearing assemblies and can be preassembled and slipped onto the ends of the crankshaft 12 when assembling the crankshaft and the frame 16. When the upper and lower bearing assemblies 90 and 80, respectively, are in place, the hydraulic pressure preload is imposed to achieve the same two beneficial efiects achieved with the press bed bearing support system 1 I, namely, holding the side frame members 18 together and prestressing the side frame 16 to minimize the stress excursion which would otherwise cause fatigue failure.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

1. In combination with a metal forming press having a frame and a press bed, a hydraulic control system comprising:

a first bearing assembly means for movably connecting said frame to the lower side of said press bed;

a second bearing assembly means for movably connecting said frame to the upper side of said press bed;

piston means associated with said first bearing assembly means; and

hydraulic chamber means operably associated with said first bearing assembly means and substantially enclosing said piston means, said hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to carry the tonnage of said press during normal operation and wherein said fluid pressure causes said first and second bearing assembly means to exert a pres sure on said frame and said press bed thereby securely fastening said press bed to said frame.

2. The hydraulic control system of claim 1 further comprising overload control means connected to said hydraulic chamber means wherein said overload control means is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload control means when said overload condition is eliminated.

3. The hydraulic control system of claim 1 wherein said first bearing assembly means comprises:

a first bearing means having an upper surface and a segmentally spherical lower surface wherein said lower side of said press bed rests on said upper surface of said first bearing means and wherein said spherical portion of said segmentally spherical lower surface of said first bearing means operably engages said piston means; and

a second bearing means having an upper surface with a cavity therein and a lower surface wherein said piston means is operably positioned in said cavity and wherein said lower surface of said second bearing means engages said frame.

4. The hydraulic control system of claim 3 wherein the upper surface of said piston means comprises a spherical cavity and wherein the shape of said spherical cavity corresponds to said shape of said spherical lower surface of said first bear ing means.

5. The hydraulic control system of claim 4 wherein said hydraulic chamber means comprises a first chamber and a second chamber, said first chamber being substantially formed by said segmentally spherical lower surface of said first bearing means and by said upper surface of said piston means and said second chamber being substantially formed by said lower surface of said piston means and by said cavity in said upper surface of said second bearing m-ans. I

6. The hydraulic control system of claim 5 further comprismg:

a third chamber connecting said first and second chambers wherein said pressures in said first and second chambers are substantially equal; and

a fourth chamber connected to said second chamber and adapted to convey a fluid under pressure to said first and second chambers wherein said fluid pressure in said first chamber substantially supports said first bearing means thereby accommodating slight movement of said press bed with respect to said frame.

7. The hydraulic control system of claim 6 wherein said second bearing assembly comprises:

a segmentally spherical third bearing means operably engaging said upper side of said press bed; and

a fourth bearing means having an upper surface operably engaging said frame and a lower surface comprising a spherical cavity which is in operable engagement with said third bearing means wherein said frame is movably connected to said press bed.

8. The hydraulic control system of claim 6 further comprising overload control means connected to said fourth chamber wherein said overload control means is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload control means when said overload condition is eliminated.

9. The hydraulic control system of claim 2 wherein said overload control means comprises:

conduit means connected to said hydraulic chamber means;

accumulator means connected to said conduit means for absorbing small changes in said fluid pressure due to momentary press overloads; and

overload valve means connected to said conduit means wherein said overload valve means causes said reduction in pressure during said overload condition.

10. The hydraulic control system of claim 9 wherein said accumulator means comprises a pneumatic-hydraulic booster.

1l. The hydraulic control system of claim 8 wherein said overload control means comprises:

accumulator means connected to said fourth chamber for absorbing small changes in said fluid pressure due to momentary press overloads; and

overload valve means connected to said conduit means wherein said overload valve means causes said reduction in pressure during said overload condition.

12. In combination with a metal forming press having a frame and a press bed, a hydraulic control system for prestressing said frame and for providing overload protection for said press comprising:

a first bearing means having an upper surface and a segmentally spherical lower surface wherein said lower side of said press bed rests on said upper surface of said first bearing means;

a second bearing means having an upper surface with a cavity therein and a lower surface wherein said lower surface of said second bearing means engages said frame;

a piston means operably positioned within said cavity of said second bearing means, said piston means having a lower surface and an upper surface, said upper surface having a cavity therein, and wherein said upper surface of said piston operably engages said segmentally spherical lower surface of said first bearing means;

a segmentally spherical third bearing means operably engaging the upper side of said press bed;

a fourth bearing means having an upper surface operably engaging said frame and a lower surface comprising a spherical cavity which is in operable engagement with said third bearing means wherein said frame is movably connected to said press bed;

a first hydraulic chamber, said first chamber being substantially formed by said lower surface of said first bearing means and by said upper surface of said piston means;

a second hydraulic chamber, said second chamber being substantially formed by said lower surface of said piston means and by said upper surface of said second bearing means;

a third hydraulic chamber connecting said first and second hydraulic chambers;

conduit means connected to said second chamber adapted to convey a liquid under pressure to said first and second chambers, said fluid pressure being sufiicient to carry the tonnage of said press during normal operation wherein said fluid pressure in said first chamber substantially supports said first bearing means thereby accommodating slight movement of said press bed with respect to said frame and wherein said fluid pressure in said first and second chambers exerts a pressure on said first, second, third and fourth bearing means thereby prestressing said frame and causing said press bed to be secured to said frame;

accumulator means connected to said conduit means for absorbing small changes in said fluid pressure due to momentary press overloads; an

overload valve means connected to said conduit means wherein said overload control valve is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload valve means when said overload condition is eliminated.

13. In combination with a metal forming press having a frame, a press bed, and a crankshaft, a hydraulic control system for prestressing said frame comprising:

a first bearing assembly means for movably connecting said frame to the lower side of said press bed;

a second bearing assembly means for movably connecting said frame to the upper side of said press bed;

piston means associated with said first bearing assembly means;

a first hydraulic chamber means operably associated with said first bearing assembly means and substantially enclosing said piston means, said first hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to carry the tonnage of said press during normal operation and wherein said fluid pressure causes said first and second bearing assembly means to exert a pressure on said frame and said press bed thereby securely fastening said press bed to said frame;

a first bearing means rotatably connected to an encircling said crankshaft;

a third bearing assembly means for movably connecting the upper portion of said first bearing means to said frame;

a fourth bearing assembly means for movably connecting the lower portion of said first bearing means to said frame; and

second hydraulic chamber means operably associated with said third bearing assembly means, said second hydraulic chamber means being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to impose a load greater than the tonnage of said press wherein said fluid pressure causes said third and fourth bearing assembly means to exert a pressure on said first bearing means and said frame thereby securely supporting said crankshaft and securely fastening said first bearing means to said frame and wherein said pressures exerted in first and second hydraulic chamber means causes a prestressing of said frame thereby eliminating stress excursions of said frame.

14. In combination with a metal forming press having a crankshaft, a hydraulic control system comprising:

a first bearing means rotatably connected to and encircling said crankshaft;

a first bearing assembly means for movably connecting the upper portion of said first bearing means to said frame;

a second bearing assembly means for movably connecting the lower portion of said first bearing means to said frame; and

hydraulic chamber means operably associated with said first bearing assembly means, said hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to impose a load greater than the tonnage of said press wherein said fluid pressure causes said first and second bearing assembly means to exert a pressure on said first bearing means and said therein.

16. The hydraulic control system of claim 15 wherein said hydraulic chamber means comprises a chamber being substantially fonned by said upper surface of said second bearing means and said lower surface of said third bearing means wherein said fluid under pressure causes said second bearing means and said second bearing assembly to prestress said frame. 

1. In combination with a metal forming press having a frame and a press bed, a hydraulic control system comprising: a first bearing assembly means for movably connecting said frame to the lower side of said press bed; a second bearing assembly means for movably connecting said frame to the upper side of said press bed; piston means associated with said first bearing assembly means; and hydraulic chamber means operably associated with said first bearing assembly means and substantially enclosing said piston means, said hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to carry the tonnage of said press during normal operation and wherein said fluid pressure causes said first and second bearing assembly means to exert a pressure on said frame and said press bed thereby securely fastening said press bed to said frame.
 2. The hydraulic control system of claim 1 further comprising overload control means connected to said hydraulic chamber means wherein said overload control means is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload control means when said oveRload condition is eliminated.
 3. The hydraulic control system of claim 1 wherein said first bearing assembly means comprises: a first bearing means having an upper surface and a segmentally spherical lower surface wherein said lower side of said press bed rests on said upper surface of said first bearing means and wherein said spherical portion of said segmentally spherical lower surface of said first bearing means operably engages said piston means; and a second bearing means having an upper surface with a cavity therein and a lower surface wherein said piston means is operably positioned in said cavity and wherein said lower surface of said second bearing means engages said frame.
 4. The hydraulic control system of claim 3 wherein the upper surface of said piston means comprises a spherical cavity and wherein the shape of said spherical cavity corresponds to said shape of said spherical lower surface of said first bearing means.
 5. The hydraulic control system of claim 4 wherein said hydraulic chamber means comprises a first chamber and a second chamber, said first chamber being substantially formed by said segmentally spherical lower surface of said first bearing means and by said upper surface of said piston means and said second chamber being substantially formed by said lower surface of said piston means and by said cavity in said upper surface of said second bearing m-ans.
 6. The hydraulic control system of claim 5 further comprising: a third chamber connecting said first and second chambers wherein said pressures in said first and second chambers are substantially equal; and a fourth chamber connected to said second chamber and adapted to convey a fluid under pressure to said first and second chambers wherein said fluid pressure in said first chamber substantially supports said first bearing means thereby accommodating slight movement of said press bed with respect to said frame.
 7. The hydraulic control system of claim 6 wherein said second bearing assembly comprises: a segmentally spherical third bearing means operably engaging said upper side of said press bed; and a fourth bearing means having an upper surface operably engaging said frame and a lower surface comprising a spherical cavity which is in operable engagement with said third bearing means wherein said frame is movably connected to said press bed.
 8. The hydraulic control system of claim 6 further comprising overload control means connected to said fourth chamber wherein said overload control means is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload control means when said overload condition is eliminated.
 9. The hydraulic control system of claim 2 wherein said overload control means comprises: conduit means connected to said hydraulic chamber means; accumulator means connected to said conduit means for absorbing small changes in said fluid pressure due to momentary press overloads; and overload valve means connected to said conduit means wherein said overload valve means causes said reduction in pressure during said overload condition.
 10. The hydraulic control system of claim 9 wherein said accumulator means comprises a pneumatic-hydraulic booster.
 11. The hydraulic control system of claim 8 wherein said overload control means comprises: accumulator means connected to said fourth chamber for absorbing small changes in said fluid pressure due to momentary press overloads; and overload valve means connected to said conduit means wherein said overload valve means causes said reduction in pressure during said overload condition.
 12. In combination with a metal forming press having a frame and a press bed, a hydraulic control system for prestressing said frame and for providing overload protection for said press comprising: a first bearing means having an upper surface and a segmentally spherical lower surface whErein said lower side of said press bed rests on said upper surface of said first bearing means; a second bearing means having an upper surface with a cavity therein and a lower surface wherein said lower surface of said second bearing means engages said frame; a piston means operably positioned within said cavity of said second bearing means, said piston means having a lower surface and an upper surface, said upper surface having a cavity therein, and wherein said upper surface of said piston operably engages said segmentally spherical lower surface of said first bearing means; a segmentally spherical third bearing means operably engaging the upper side of said press bed; a fourth bearing means having an upper surface operably engaging said frame and a lower surface comprising a spherical cavity which is in operable engagement with said third bearing means wherein said frame is movably connected to said press bed; a first hydraulic chamber, said first chamber being substantially formed by said lower surface of said first bearing means and by said upper surface of said piston means; a second hydraulic chamber, said second chamber being substantially formed by said lower surface of said piston means and by said upper surface of said second bearing means; a third hydraulic chamber connecting said first and second hydraulic chambers; conduit means connected to said second chamber adapted to convey a liquid under pressure to said first and second chambers, said fluid pressure being sufficient to carry the tonnage of said press during normal operation wherein said fluid pressure in said first chamber substantially supports said first bearing means thereby accommodating slight movement of said press bed with respect to said frame and wherein said fluid pressure in said first and second chambers exerts a pressure on said first, second, third and fourth bearing means thereby prestressing said frame and causing said press bed to be secured to said frame; accumulator means connected to said conduit means for absorbing small changes in said fluid pressure due to momentary press overloads; an overload valve means connected to said conduit means wherein said overload control valve is adapted to reduce said fluid pressure during an overload condition of said press and wherein said fluid pressure is restored by said overload valve means when said overload condition is eliminated.
 13. In combination with a metal forming press having a frame, a press bed, and a crankshaft, a hydraulic control system for prestressing said frame comprising: a first bearing assembly means for movably connecting said frame to the lower side of said press bed; a second bearing assembly means for movably connecting said frame to the upper side of said press bed; piston means associated with said first bearing assembly means; a first hydraulic chamber means operably associated with said first bearing assembly means and substantially enclosing said piston means, said first hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to carry the tonnage of said press during normal operation and wherein said fluid pressure causes said first and second bearing assembly means to exert a pressure on said frame and said press bed thereby securely fastening said press bed to said frame; a first bearing means rotatably connected to an encircling said crankshaft; a third bearing assembly means for movably connecting the upper portion of said first bearing means to said frame; a fourth bearing assembly means for movably connecting the lower portion of said first bearing means to said frame; and second hydraulic chamber means operably associated with said third bearing assembly means, said second hydraulic chamber means being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to impose a load greater than the tonnage of said press wherein said fluid pRessure causes said third and fourth bearing assembly means to exert a pressure on said first bearing means and said frame thereby securely supporting said crankshaft and securely fastening said first bearing means to said frame and wherein said pressures exerted in first and second hydraulic chamber means causes a prestressing of said frame thereby eliminating stress excursions of said frame.
 14. In combination with a metal forming press having a crankshaft, a hydraulic control system comprising: a first bearing means rotatably connected to and encircling said crankshaft; a first bearing assembly means for movably connecting the upper portion of said first bearing means to said frame; a second bearing assembly means for movably connecting the lower portion of said first bearing means to said frame; and hydraulic chamber means operably associated with said first bearing assembly means, said hydraulic chamber being adapted to convey a fluid under pressure wherein said fluid pressure is sufficient to impose a load greater than the tonnage of said press wherein said fluid pressure causes said first and second bearing assembly means to exert a pressure on said first bearing means and said frame thereby securely supporting said crankshaft and securely fastening said first bearing means to said frame.
 15. The hydraulic control system of claim 14 wherein said first bearing assembly comprises: a second bearing means having a lower surface with a cavity therein, said cavity being adapted to movably engage said upper portion of said first bearing means; and a third bearing means comprising an upper surface adapted to engage said frame and a lower surface having a cavity therein.
 16. The hydraulic control system of claim 15 wherein said hydraulic chamber means comprises a chamber being substantially formed by said upper surface of said second bearing means and said lower surface of said third bearing means wherein said fluid under pressure causes said second bearing means and said second bearing assembly to prestress said frame. 